Published in Nature Communications, the study is the largest of its kind and was led by Walter and Eliza Hall Institute computational biologists Professor Tony Papenfuss, Dr Daniel Cameron and Mr Leon Di Stefano.
The new study reveals the world's top genomic rearrangement detection tools providing summaries on their performance and recommendations for use. Dr Cameron said the study could ultimately help clinicians determine the best treatments for their patients.
"Basically, you have to understand what is going wrong before you can work out how to fix the problem. In the context of cancer for instance, an understanding of the genetic mutations driving tumour growth could help oncologists determine the most appropriate treatment for their patients," he said.
To determine the best genomic rearrangement detection methods, the researchers comprehensively tested 12 of the most widely used tools to see which ones could accurately identify the differences between a patient's genetic information and the standard human reference genome. The findings revealed that a tool called GRIDSS, developed by Professor Papenfuss and Dr Cameron, was one of the best performing options, most accurately able to detect DNA rearrangements.
Dr Cameron said the study would not have been possible without the Institute's high-performance computing resource.
"Over the course of two years, we tested 12 of the most popular genomic rearrangement detection tools, generating more than 50 terabytes of data, to determine which tools perform well, and when they perform badly. Without these computing resources, we estimate the study would have taken us more than ten years," he said.
The Institute's Theme Leader for Computational Biology Professor Papenfuss said computational methods were required, more than ever before, for making sense of vast and complex datasets being generated from research.
"Computational studies like this one keep the field up to date with best practice approaches for data analysis. This particular study provides a comprehensive resource for users of genomic rearrangement detection methods, as well as developers in the field. It will also help to direct the next iteration of genomic rearrangement tool development at the Institute," he said.
As new experimental techniques and DNA sequencing machines become available, the very nature of the data they generate is changing. Professor Papenfuss said that older analysis tools, while heavily cited and widely used, could lead to erroneous interpretations if used on data produced by the latest DNA sequencing machines. "This is why it is so important for researchers to find the right match between the analysis tool and dataset at hand," he said.
From Science Daily
Jul 27, 2019
Production sites of stars are rare
Astronomers using the Nobeyama Radio Obeservatory (NRO) 45-m telescope found that high-density gas, the material for stars, accounts for only 3% of the total mass of gas distributed in the Milky Way. This result provides key information for understanding the unexpectedly low production rate of stars.
Stars are born in gas clouds. The high-density gas pockets form in the extended, low-density gas clouds, and stars form in the very dense gas cores which evolve within the high-density gas. However, observations of distant galaxies detected 1000 times fewer stars than the production value expected from the total amount of low-density gas. To interpret the discrepancy, observations which detect both of the high-density and low-density gas with high-spatial resolution and wide area coverage were needed. However, such observations are difficult, because the high-density gas structures are dozens of times smaller than the low-density gas structures.
The Milky Way survey project "FUGIN" conducted using the NRO 45-m telescope and the multi-beam receiver FOREST overcame these difficulties. Kazufumi Torii, a project assistant professor at NAOJ, and his team analyzed the big data obtained in the FUGIN project, and measured the accurate masses of the low-density and high-density gas for a large span of 20,000 light-years along the Milky Way. They revealed for the first time that the high-density gas accounts for only 3% of the total gas.
These results imply the production rate of high-density gas in the low-density gas clouds is small, creating only a small number of opportunities to form stars. The researcher team will continue working on the FUGIN data to investigate the cause of inefficient formation of the high-density gas.
These observation results were published as K. Torii et al. "FOREST Unbiased Galactic plane Imaging survey with the Nobeyama 45 m telescope (FUGIN). V. Dense gas mass fraction of molecular gas in the Galactic plane" as an on-line paper of the Publications of the Astronomical Society of Japan on 2019 Apr., and will be published as a special issue.
From Science Daily
Stars are born in gas clouds. The high-density gas pockets form in the extended, low-density gas clouds, and stars form in the very dense gas cores which evolve within the high-density gas. However, observations of distant galaxies detected 1000 times fewer stars than the production value expected from the total amount of low-density gas. To interpret the discrepancy, observations which detect both of the high-density and low-density gas with high-spatial resolution and wide area coverage were needed. However, such observations are difficult, because the high-density gas structures are dozens of times smaller than the low-density gas structures.
The Milky Way survey project "FUGIN" conducted using the NRO 45-m telescope and the multi-beam receiver FOREST overcame these difficulties. Kazufumi Torii, a project assistant professor at NAOJ, and his team analyzed the big data obtained in the FUGIN project, and measured the accurate masses of the low-density and high-density gas for a large span of 20,000 light-years along the Milky Way. They revealed for the first time that the high-density gas accounts for only 3% of the total gas.
These results imply the production rate of high-density gas in the low-density gas clouds is small, creating only a small number of opportunities to form stars. The researcher team will continue working on the FUGIN data to investigate the cause of inefficient formation of the high-density gas.
These observation results were published as K. Torii et al. "FOREST Unbiased Galactic plane Imaging survey with the Nobeyama 45 m telescope (FUGIN). V. Dense gas mass fraction of molecular gas in the Galactic plane" as an on-line paper of the Publications of the Astronomical Society of Japan on 2019 Apr., and will be published as a special issue.
From Science Daily
Jul 26, 2019
Underwater glacial melting is occurring at higher rates than modeling predicts
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| LeConte Glacier, Alaska. |
In a National Science Foundation-funded project, a team of scientists, led by University of Oregon oceanographer Dave Sutherland, studied the subsurface melting of the LeConte Glacier, which flows into LeConte Bay south of Juneau, Alaska.
The team's findings, which could lead to improved forecasting of climate-driven sea level rise, were published in the July 26 issue of the journal Science.
Direct melting measurements previously have been made on ice shelves in Antarctica by boring through to the ice-ocean interface beneath. In the case of vertical-face glaciers terminating at the ocean, however, those techniques are not available.
"We don't have that platform to be able to access the ice in this way," said Sutherland, a professor in the UO's Department of Earth Sciences. "Tidewater glaciers are always calving and moving very rapidly, and you don't want to take a boat up there too closely."
Most previous research on the underwater melting of glaciers relied on theoretical modeling, measuring conditions near the glaciers and then applying theory to predict melt rates. But this theory had never been directly tested.
"This theory is used widely in our field," said study co-author Rebecca H. Jackson, an oceanographer at Rutgers University who was a postdoctoral researcher at Oregon State University during the project. "It's used in glacier models to study questions like: how will the glacier respond if the ocean warms by one or two degrees?"
To test these models in the field, the research team of oceanographers and glaciologists deployed a multibeam sonar to scan the glacier's ocean-ice interface from a fishing vessel six times in August 2016 and five times in May 2017.
The sonar allowed the team to image and profile large swaths of the underwater ice, where the glacier drains from the Stikine Icefield. Also gathered were data on the temperature, salinity and velocity of the water downstream from the glacier, which allowed the researchers to estimate the meltwater flow.
They then looked for changes in melt patterns that occurred between the August and May measurements.
"We measured both the ocean properties in front of the glacier and the melt rates, and we found that they are not related in the way we expected," Jackson said. "These two sets of measurements show that melt rates are significantly, sometimes up to a factor of 100, higher than existing theory would predict."
There are two main categories of glacial melt: discharge-driven and ambient melt. Subglacial discharge occurs when large volumes, or plumes, of buoyant meltwater are released below the glacier. The plume combines with surrounding water to pick up speed and volume as it rises up swiftly against the glacial face. The current steadily eats away from the glacier face, undercutting the glacier before eventually diffusing into the surrounding waters.
Most previous studies of ice-ocean interactions have focused on these discharge plumes. The plumes, however, typically affect only a narrow area of the glacier face, while ambient melt instead covers the rest of the glacier face.
Predictions have estimated ambient melt to be 10-100 times less than the discharge melt, and, as such, it is often disregarded as insignificant, said Sutherland, who heads the UO's Oceans and Ice Lab.
The research team found that submarine melt rates were high across the glacier's face over both of the seasons surveyed, and that the melt rate increases from spring to summer.
While the study focused on one marine-terminating glacier, Jackson said, the new approach should be useful to any researchers who are studying melt rates at other glaciers. That would help to improve projections of global sea level rise, she added.
Read more at Science Daily
Scientists find clue to 'maternal instinct'
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| Lab mouse and pups |
"Many researchers have attempted to investigate the difference between the oxytocin system in females versus males, but no one has successfully found conclusive evidence until now. Our discovery was a big surprise," said Ryoichi Teruyama, LSU Department of Biological Sciences associate professor, who led this study published in PLOS ONE.
The oxytocin receptor cells are present in the brain area thought to be involved in the regulation of maternal behavior. Moreover, the expression of oxytocin receptors in these cells are only present when estrogen is also present. These imply that these cells are involved in inducing maternal behavior. In addition, it confirms what many recent human studies have shown: there is a connection between an altered expression of oxytocin receptors and postpartum depression.
Postpartum depression contributes to poor maternal health and has negative effects on a child's development. A number of studies have found that children of depressed mothers are at risk for a wide range of cognitive, emotional, behavioral and medical problems. Therefore, postpartum depression is a major public health concern that has significant adverse effects on both mother and child. About 10 to 20 percent of women experience postpartum depression after childbirth.
This new discovery that occurred at LSU opens doors to potential new treatments and drugs for postpartum depression targeting oxytocin receptor cells.
"I think our discovery could be universal to all mammals that exhibit maternal behavior, including humans," Teruyama said.
Student researchers
Study co-author Ryan LeBlanc from Denham Springs was an undergraduate student researcher at LSU whose work was instrumental to this discovery. However, he had little previous research experience before joining Teruyama's lab.
Teruyama recalled that when LeBlanc first approached him to be his mentor, he asked him about his hobbies. LeBlanc said he liked to build plastic models of battleships.
"I certainly don't know much about battleship plastic models, but anyone who can assemble 500 to 2,000 plastic parts into models must be persistent, focused and exceedingly careful. I accepted him gladly thinking he is going to find something extraordinary, and I was right," Teruyama said.
LeBlanc took on the tedious task of finding and marking the exact location of thousands of oxytocin receptor cells with a red pen. He spent more than a month identifying the cells, which was instrumental to this discovery.
Read more at Science Daily
Einstein's general relativity theory is questioned but still stands for now
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| Black hole illustration |
"Einstein's right, at least for now," said Ghez, a co-lead author of the research. "We can absolutely rule out Newton's law of gravity. Our observations are consistent with Einstein's theory of general relativity. However, his theory is definitely showing vulnerability. It cannot fully explain gravity inside a black hole, and at some point we will need to move beyond Einstein's theory to a more comprehensive theory of gravity that explains what a black hole is."
Einstein's 1915 theory of general relativity holds that what we perceive as the force of gravity arises from the curvature of space and time. The scientist proposed that objects such as the sun and the Earth change this geometry. Einstein's theory is the best description of how gravity works, said Ghez, whose UCLA-led team of astronomers has made direct measurements of the phenomenon near a supermassive black hole -- research Ghez describes as "extreme astrophysics."
The laws of physics, including gravity, should be valid everywhere in the universe, said Ghez, who added that her research team is one of only two groups in the world to watch a star known as S0-2 make a complete orbit in three dimensions around the supermassive black hole at the center of the Milky Way. The full orbit takes 16 years, and the black hole's mass is about four million times that of the sun.
The researchers say their work is the most detailed study ever conducted into the supermassive black hole and Einstein's theory of general relativity.
The key data in the research were spectra that Ghez's team analyzed this April, May and September as her "favorite star" made its closest approach to the enormous black hole. Spectra, which Ghez described as the "rainbow of light" from stars, show the intensity of light and offer important information about the star from which the light travels. Spectra also show the composition of the star. These data were combined with measurements Ghez and her team have made over the last 24 years.
Spectra -- collected at the W.M. Keck Observatory in Hawaii using a spectrograph built at UCLA by a team led by colleague James Larkin -- provide the third dimension, revealing the star's motion at a level of precision not previously attained. (Images of the star the researchers took at the Keck Observatory provide the two other dimensions.) Larkin's instrument takes light from a star and disperses it, similar to the way raindrops disperse light from the sun to create a rainbow, Ghez said.
"What's so special about S0-2 is we have its complete orbit in three dimensions," said Ghez, who holds the Lauren B. Leichtman and Arthur E. Levine Chair in Astrophysics. "That's what gives us the entry ticket into the tests of general relativity. We asked how gravity behaves near a supermassive black hole and whether Einstein's theory is telling us the full story. Seeing stars go through their complete orbit provides the first opportunity to test fundamental physics using the motions of these stars."
Ghez's research team was able to see the co-mingling of space and time near the supermassive black hole. "In Newton's version of gravity, space and time are separate, and do not co-mingle; under Einstein, they get completely co-mingled near a black hole," she said.
"Making a measurement of such fundamental importance has required years of patient observing, enabled by state-of-the-art technology," said Richard Green, director of the National Science Foundation's division of astronomical sciences. For more than two decades, the division has supported Ghez, along with several of the technical elements critical to the research team's discovery. "Through their rigorous efforts, Ghez and her collaborators have produced a high-significance validation of Einstein's idea about strong gravity."
Keck Observatory Director Hilton Lewis called Ghez "one of our most passionate and tenacious Keck users." "Her latest groundbreaking research," he said, "is the culmination of unwavering commitment over the past two decades to unlock the mysteries of the supermassive black hole at the center of our Milky Way galaxy."
The researchers studied photons -- particles of light -- as they traveled from S0-2 to Earth. S0-2 moves around the black hole at blistering speeds of more than 16 million miles per hour at its closest approach. Einstein had reported that in this region close to the black hole, photons have to do extra work. Their wavelength as they leave the star depends not only on how fast the star is moving, but also on how much energy the photons expend to escape the black hole's powerful gravitational field. Near a black hole, gravity is much stronger than on Earth.
Ghez was given the opportunity to present partial data last summer, but chose not to so that her team could thoroughly analyze the data first. "We're learning how gravity works. It's one of four fundamental forces and the one we have tested the least," she said. "There are many regions where we just haven't asked, how does gravity work here? It's easy to be overconfident and there are many ways to misinterpret the data, many ways that small errors can accumulate into significant mistakes, which is why we did not rush our analysis."
Ghez, a 2008 recipient of the MacArthur "Genius" Fellowship, studies more than 3,000 stars that orbit the supermassive black hole. Hundreds of them are young, she said, in a region where astronomers did not expect to see them.
It takes 26,000 years for the photons from S0-2 to reach Earth. "We're so excited, and have been preparing for years to make these measurements," said Ghez, who directs the UCLA Galactic Center Group. "For us, it's visceral, it's now -- but it actually happened 26,000 years ago!"
This is the first of many tests of general relativity Ghez's research team will conduct on stars near the supermassive black hole. Among the stars that most interest her is S0-102, which has the shortest orbit, taking 11 1/2 years to complete a full orbit around the black hole. Most of the stars Ghez studies have orbits of much longer than a human lifespan.
Ghez's team took measurements about every four nights during crucial periods in 2018 using the Keck Observatory -- which sits atop Hawaii's dormant Mauna Kea volcano and houses one of the world's largest and premier optical and infrared telescopes. Measurements are also taken with an optical-infrared telescope at Gemini Observatory and Subaru Telescope, also in Hawaii. She and her team have used these telescopes both on site in Hawaii and remotely from an observation room in UCLA's department of physics and astronomy.
Black holes have such high density that nothing can escape their gravitational pull, not even light. (They cannot be seen directly, but their influence on nearby stars is visible and provides a signature. Once something crosses the "event horizon" of a black hole, it will not be able to escape. However, the star S0-2 is still rather far from the event horizon, even at its closest approach, so its photons do not get pulled in.)
Ghez's co-authors include Tuan Do, lead author of the Science paper, a UCLA research scientist and deputy director of the UCLA Galactic Center Group; Aurelien Hees, a former UCLA postdoctoral scholar, now a researcher at the Paris Observatory; Mark Morris, UCLA professor of physics and astronomy; Eric Becklin, UCLA professor emeritus of physics and astronomy; Smadar Naoz, UCLA assistant professor of physics and astronomy; Jessica Lu, a former UCLA graduate student who is now a UC Berkeley assistant professor of astronomy; UCLA graduate student Devin Chu; Greg Martinez, UCLA project scientist; Shoko Sakai, a UCLA research scientist; Shogo Nishiyama, associate professor with Japan's Miyagi University of Education; and Rainer Schoedel, a researcher with Spain's Instituto de Astrofsica de Andalucia.
Read more at Science Daily
Strange bacteria hint at ancient origin of photosynthesis
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| Leaf in sunlight |
The finding could mean the evolution of photosynthesis needs a rethink, turning traditional ideas on their head.
Photosynthesis is the ability to use the Sun's energy to produce sugars via chemical reactions. Plants, algae, and some bacteria today perform 'oxygenic' photosynthesis, which splits water into oxygen and hydrogen to power the process, releasing oxygen as a waste product.
Some bacteria instead perform 'anoxygenic' photosynthesis, a version that uses molecules other than water to power the process and does not release oxygen.
Scientists have always assumed that anoxygenic photosynthesis is more 'primitive', and that oxygenic photosynthesis evolved from it. Under this view, anoxygenic photosynthesis emerged about 3.5 billion years ago and oxygenic photosynthesis evolved a billion years later.
However, by analysing structures inside an ancient type of bacteria, Imperial College London researchers have suggested that a key step in oxygenic photosynthesis may have already been possible a billion years before commonly thought.
The new research is published in the journal Trends in Plant Science.
Lead author of the study, Dr Tanai Cardona from the Department of Life Sciences at Imperial, said: "We're beginning to see that much of the established story about the evolution of photosynthesis is not supported by the real data we obtain about the structure and functioning of early bacterial photosynthesis systems."
The bacteria they studied, Heliobacterium modesticaldum, is found around hot springs, soils and waterlogged fields, where it performs anoxygenic photosynthesis. It is very distantly related to cyanobacteria, the main bacteria that performs oxygenic photosynthesis today.
It is so distantly related that it last had a 'common ancestor' with cyanobacteria billions of years ago. This means that any traits the two bacteria share are likely to also have been present in the ancient bacteria that gave rise to them both.
By analysing the structures that both H. modesticaldum and modern cyanobacteria use to perform their different types of photosynthesis, Dr Cardona found striking similarities.
Both structures contain a site that cyanobacteria and plants exclusively use to split water -- the first crucial step in oxygenic photosynthesis.
The evolution of cyanobacteria is usually assumed to also be the first appearance of oxygenic photosynthesis, but the fact that H. modesticaldum contains a similar site means that the building blocks for oxygenic photosynthesis are likely much more ancient than thought, as old as photosynthesis itself, and therefore could have arisen much earlier in Earth's history.
Dr Cardona also suggests that this might mean oxygenic photosynthesis was not the product of a billion years of evolution from anoxygenic photosynthesis, but could have been a trait that evolved much sooner, if not first.
Dr Cardona said: "This result helps explain in fantastic detail why the systems responsible for photosynthesis and oxygen production are the way they are today- but for it to make sense it requires a change of perspective in the way we view the evolution of photosynthesis.
"Under the traditional view -- that anoxygenic photosynthesis evolved first and was the only type for about a billion years or more before oxygenic photosynthesis evolved -- these structures should not exist at all in this type of bacteria."
Read more at Science Daily
Jul 25, 2019
New telescope gives peek at the birth of the universe
The Square Kilometre Array (SKA) is set to become the largest radio telescope on Earth. Bielefeld University researchers together with the Max Planck Institute for Radio Astronomy (MPIfR) and international partners have now examined the SKA-MPG telescope -- a prototype for the part of the SKA that receives signals in the mid-frequency range. The study, published today (24 July) in the journal Monthly Notices of the Royal Astronomical Society, shows that the telescope is not only a prototype to test the SKA design, but can also be used on its own to provide insights into the origin of the Universe. The German Federal Ministry of Education and Research (BMBF) is funding the work on the SKA-MPG through a joint research project coordinated by Bielefeld University.
'The SKA-MPG telescope in South Africa will help us to understand the cosmic background Radiation,' says Dr Aritra Basu, lead author of the study and physicist in Bielefeld University's Astroparticle Physics and Cosmology Working Group. The cosmic background radiation is light in the microwave range that was produced shortly after the Big Bang, and exploring it provides information about the origin of the Universe. 'However, measurements of the cosmic background radiation are distorted by other effects in the foreground, such as ultrafast electrons in the magnetic field of the Milky Way. In order to measure cosmic background radiation, we need to know more about these effects. Our study shows that the new telescope is excellent for investigating foreground radiation with ultra precision,' says Basu.
The SKA-MPG telescope was jointly developed by the Max Planck Institute for Radio Astronomy (MPIfR) in Bonn and MT-Mechatronics GmbH. The abbreviation 'MPG' stands for the Max Planck Society, which is funding the telescope. The radio telescope has a diameter of 15 metres and can receive signals between 1.7 and 3.5 GHz. It is currently being assembled in the South Africa's Karoo desert. Gundolf Wieching of the MPIfR, project leader of the telescope, expects first regular scientific use in autumn 2019.
The radio telescope is primarily designed as a prototype for a part of the SKA that receives signals from a medium radio frequency range. If the prototype performs well in a series of tests, around 200 such telescopes will be built for the SKA in South Africa. The SKA will observe medium as well as low radio frequencies. This second instrument will consist of thousands of small radio antennae that can be combined to simulate a huge radio telescope. The two parts of the SKA will then collect Signals over one square kilometre in Australia and South Africa -- hence the name 'Square Kilometre Array'. 'Even with our prototype, we are able to look deep into the Universe thanks to a clever design for the telescope and new developments in receiver and backend technology,' says Dr Hans-Rainer Klöckner, astrophysicist at the MPIfR. 'I am curious to see what we will discover once 200 of these telescopes are synchronised for the SKA.' The SKA will be used, for example, to explore gravitational waves and dark energy, or to test Einstein's theory of relativity under extreme conditions.
The SKA will be the first global science organisation with locations on three continents: Australia, Africa, and Europe. In addition, data centres are being set up around the world. A special challenge lies in dealing with the enormous volume of data: the SKA will collect over 600 petabytes of observation data per year -- equivalent to the storage capacity of more than half a million laptops.
Read more at Science Daily
'The SKA-MPG telescope in South Africa will help us to understand the cosmic background Radiation,' says Dr Aritra Basu, lead author of the study and physicist in Bielefeld University's Astroparticle Physics and Cosmology Working Group. The cosmic background radiation is light in the microwave range that was produced shortly after the Big Bang, and exploring it provides information about the origin of the Universe. 'However, measurements of the cosmic background radiation are distorted by other effects in the foreground, such as ultrafast electrons in the magnetic field of the Milky Way. In order to measure cosmic background radiation, we need to know more about these effects. Our study shows that the new telescope is excellent for investigating foreground radiation with ultra precision,' says Basu.
The SKA-MPG telescope was jointly developed by the Max Planck Institute for Radio Astronomy (MPIfR) in Bonn and MT-Mechatronics GmbH. The abbreviation 'MPG' stands for the Max Planck Society, which is funding the telescope. The radio telescope has a diameter of 15 metres and can receive signals between 1.7 and 3.5 GHz. It is currently being assembled in the South Africa's Karoo desert. Gundolf Wieching of the MPIfR, project leader of the telescope, expects first regular scientific use in autumn 2019.
The radio telescope is primarily designed as a prototype for a part of the SKA that receives signals from a medium radio frequency range. If the prototype performs well in a series of tests, around 200 such telescopes will be built for the SKA in South Africa. The SKA will observe medium as well as low radio frequencies. This second instrument will consist of thousands of small radio antennae that can be combined to simulate a huge radio telescope. The two parts of the SKA will then collect Signals over one square kilometre in Australia and South Africa -- hence the name 'Square Kilometre Array'. 'Even with our prototype, we are able to look deep into the Universe thanks to a clever design for the telescope and new developments in receiver and backend technology,' says Dr Hans-Rainer Klöckner, astrophysicist at the MPIfR. 'I am curious to see what we will discover once 200 of these telescopes are synchronised for the SKA.' The SKA will be used, for example, to explore gravitational waves and dark energy, or to test Einstein's theory of relativity under extreme conditions.
The SKA will be the first global science organisation with locations on three continents: Australia, Africa, and Europe. In addition, data centres are being set up around the world. A special challenge lies in dealing with the enormous volume of data: the SKA will collect over 600 petabytes of observation data per year -- equivalent to the storage capacity of more than half a million laptops.
Read more at Science Daily
Cold, dry planets could have a lot of hurricanes
Nearly every atmospheric science textbook ever written will say that hurricanes are an inherently wet phenomenon -- they use warm, moist air for fuel. But according to new simulations, the storms can also form in very cold, dry climates.
A climate as cold and dry as the one in the study is unlikely to ever become the norm on Earth, especially as climate change is making the world warmer and wetter. But the findings could have implications for storms on other planets and for the intrinsic properties of hurricanes that most scientists and educators currently believe to be true.
"We have theories for how hurricanes work at temperatures that we're used to experiencing on Earth, and theoretically, they should still apply if we move to a colder and drier climate," said Dan Chavas, an assistant professor of earth, atmospheric and planetary sciences at Purdue University. "We wanted to know if hurricanes really need water. And we've shown that they don't -- but in a very different world."
In the world we live in now, hurricanes need water. When they reach land, they die because they run of out the water they evaporate for energy -- but that doesn't have to be the case. The findings were published in the Journal of the Atmospheric Sciences.
"Just because there isn't something changing phase between liquid and vapor doesn't mean a hurricane can't form," Chavas said.
In collaboration with Timothy Cronin, an assistant professor of atmospheric science at MIT, he used a computer model that mimics a very basic atmosphere and constantly generates hurricanes. In a general hurricane scenario, this looks like a box with ocean at the bottom, but Chavas tweaked it to dry out the surface or cool it below temperatures that usually generate hurricanes.
The coldest simulations were run at 240 degrees Kelvin (-28 F) and produced a shocking number of cyclones. These cold, dry storms were generally smaller and weaker than the hurricanes on Earth, but they formed at a higher frequency.
As the temperature drops, the air can hold less water, which explains why cold temperatures and dry surfaces yield similar results in experiments. At 240 degrees K, air can hold roughly 100 times less water vapor than at temperatures typical of the modern tropics.
Interestingly, there is a range of moderate temperatures and moisture levels in which no cyclones formed at all. From 250 to 270 degrees Kelvin (-10 F to 26 F), no hurricanes formed, although the researchers aren't sure why. At 280 Kelvin (44 F), the atmosphere filled again with cyclones.
"Maybe that means there are ideal regimes for hurricanes to exist and the current world we live in is one," Chavas said. "Or you could be in another world where there's no water, but it's still capable of producing many hurricanes. When people are considering whether we could live on a dry, rocky planet like Mars, this could be something to consider."
Read more at Science Daily
A climate as cold and dry as the one in the study is unlikely to ever become the norm on Earth, especially as climate change is making the world warmer and wetter. But the findings could have implications for storms on other planets and for the intrinsic properties of hurricanes that most scientists and educators currently believe to be true.
"We have theories for how hurricanes work at temperatures that we're used to experiencing on Earth, and theoretically, they should still apply if we move to a colder and drier climate," said Dan Chavas, an assistant professor of earth, atmospheric and planetary sciences at Purdue University. "We wanted to know if hurricanes really need water. And we've shown that they don't -- but in a very different world."
In the world we live in now, hurricanes need water. When they reach land, they die because they run of out the water they evaporate for energy -- but that doesn't have to be the case. The findings were published in the Journal of the Atmospheric Sciences.
"Just because there isn't something changing phase between liquid and vapor doesn't mean a hurricane can't form," Chavas said.
In collaboration with Timothy Cronin, an assistant professor of atmospheric science at MIT, he used a computer model that mimics a very basic atmosphere and constantly generates hurricanes. In a general hurricane scenario, this looks like a box with ocean at the bottom, but Chavas tweaked it to dry out the surface or cool it below temperatures that usually generate hurricanes.
The coldest simulations were run at 240 degrees Kelvin (-28 F) and produced a shocking number of cyclones. These cold, dry storms were generally smaller and weaker than the hurricanes on Earth, but they formed at a higher frequency.
As the temperature drops, the air can hold less water, which explains why cold temperatures and dry surfaces yield similar results in experiments. At 240 degrees K, air can hold roughly 100 times less water vapor than at temperatures typical of the modern tropics.
Interestingly, there is a range of moderate temperatures and moisture levels in which no cyclones formed at all. From 250 to 270 degrees Kelvin (-10 F to 26 F), no hurricanes formed, although the researchers aren't sure why. At 280 Kelvin (44 F), the atmosphere filled again with cyclones.
"Maybe that means there are ideal regimes for hurricanes to exist and the current world we live in is one," Chavas said. "Or you could be in another world where there's no water, but it's still capable of producing many hurricanes. When people are considering whether we could live on a dry, rocky planet like Mars, this could be something to consider."
Read more at Science Daily
Fastest eclipsing binary, a valuable target for gravitational wave studies
Observations made with a new instrument developed for use at the 2.1-meter (84-inch) telescope at the National Science Foundation's Kitt Peak National Observatory have led to the discovery of the fastest eclipsing white dwarf binary yet known. Clocking in with an orbital period of only 6.91 minutes, the rapidly orbiting stars are expected to be one of the strongest sources of gravitational waves detectable with LISA, the future space-based gravitational wave detector.
The Dense "Afterlives" of Stars
After expanding into a red giant at the end of its life, a star like the Sun will eventually evolve into a dense white dwarf, an object with a mass like that of the Sun squashed down to a size comparable to Earth. Similarly, as binary stars evolve, they can engulf their companion in the red giant phase and spiral close together, eventually leaving behind a close white dwarf binary. White dwarf binaries with very tight orbits are expected to be strong sources of gravitational wave radiation. Although anticipated to be relatively common, such systems have proven elusive, with only a few identified to date.
Record-setting White Dwarf Binary
A new survey of the night sky, currently underway at Palomar Observatory and Kitt Peak National Observatory, is changing this situation.
Each night, Caltech's Zwicky Transient Facility (ZTF), a survey that uses the 48-inch telescope at Palomar Observatory, scans the sky for objects that move, blink, or otherwise vary in brightness. Promising candidates are followed up with a new instrument, the Kitt Peak 84-inch Electron Multiplying Demonstrator (KPED), at the Kitt Peak 2.1-meter telescope to identify short period eclipsing binaries. KPED is designed to measure with speed and sensitivity the changing brightness of celestial sources.
This approach has led to the discovery of ZTF J1539+5027 (or J1539 for short), a white dwarf eclipsing binary with the shortest period known to date, a mere 6.91 minutes. The stars orbit so close together that the entire system could fit within the diameter of the planet Saturn.
"As the dimmer star passes in front of the brighter one, it blocks most of the light, resulting in the seven-minute blinking pattern we see in the ZTF data," explains Caltech graduate student Kevin Burdge, lead author of the paper reporting the discovery, which appears in the today's issue of the journal Nature.
A Strong Source of Gravitational Waves
Closely orbiting white dwarfs are predicted to spiral together closer and faster, as the system loses energy by emitting gravitational waves. J1539's orbit is so tight that its orbital period is predicted to become measurably shorter after only a few years. Burdge's team was able to confirm the prediction from general relativity of a shrinking orbit, by comparing their new results with archival data acquired over the past ten years.
J1539 is a rare gem. It is one of only a few known sources of gravitational waves -- ripples in space and time -- that will be detected by the future European space mission LISA (Laser Interferometer Space Antenna), which is expected to launch in 2034. LISA, in which NASA plays a role, will be similar to the National Science Foundation's ground-based LIGO (Laser Interferometer Gravitational-wave Observatory), which made history in 2015 by making the first direct detection of gravitational waves from a pair of colliding black holes. LISA will detect gravitational waves from space at lower frequencies. J1539 is well matched to LISA; the 4.8 mHz gravitational wave frequency of J1539 is close to the peak of LISA's sensitivity.
Discoveries Continue for Historic Telescope
Kitt Peak's 2.1-meter telescope, the second major telescope to be constructed at the site, has been in continuous operation since 1964. Its history includes many important discoveries in astrophysics, such as the Lyman-alpha forest in quasar spectra, the first gravitational lens by a galaxy, the first pulsating white dwarf, and the first comprehensive study of the binary frequency of stars like the Sun. The latest result continues its venerable track record.
Lori Allen, Director of Kitt Peak National Observatory and Acting Director of NOAO says, "We're thrilled to see that our 2.1-meter telescope, now more than 50 years old, remains a powerful platform for discovery."
"These wonderful observations are further proof that cutting-edge science can be done on modest-sized telescopes like the 2.1-meter in the modern era," adds Chris Davis, NSF Program Officer for NOAO.
More Thrills Ahead!
As remarkable as it is, J1539 was discovered with only a small portion of the data expected from ZTF. It was found in the ZTF team's initial analysis of 10 million sources, whereas the project will eventually study more than a billion stars.
Read more at Science Daily
The Dense "Afterlives" of Stars
After expanding into a red giant at the end of its life, a star like the Sun will eventually evolve into a dense white dwarf, an object with a mass like that of the Sun squashed down to a size comparable to Earth. Similarly, as binary stars evolve, they can engulf their companion in the red giant phase and spiral close together, eventually leaving behind a close white dwarf binary. White dwarf binaries with very tight orbits are expected to be strong sources of gravitational wave radiation. Although anticipated to be relatively common, such systems have proven elusive, with only a few identified to date.
Record-setting White Dwarf Binary
A new survey of the night sky, currently underway at Palomar Observatory and Kitt Peak National Observatory, is changing this situation.
Each night, Caltech's Zwicky Transient Facility (ZTF), a survey that uses the 48-inch telescope at Palomar Observatory, scans the sky for objects that move, blink, or otherwise vary in brightness. Promising candidates are followed up with a new instrument, the Kitt Peak 84-inch Electron Multiplying Demonstrator (KPED), at the Kitt Peak 2.1-meter telescope to identify short period eclipsing binaries. KPED is designed to measure with speed and sensitivity the changing brightness of celestial sources.
This approach has led to the discovery of ZTF J1539+5027 (or J1539 for short), a white dwarf eclipsing binary with the shortest period known to date, a mere 6.91 minutes. The stars orbit so close together that the entire system could fit within the diameter of the planet Saturn.
"As the dimmer star passes in front of the brighter one, it blocks most of the light, resulting in the seven-minute blinking pattern we see in the ZTF data," explains Caltech graduate student Kevin Burdge, lead author of the paper reporting the discovery, which appears in the today's issue of the journal Nature.
A Strong Source of Gravitational Waves
Closely orbiting white dwarfs are predicted to spiral together closer and faster, as the system loses energy by emitting gravitational waves. J1539's orbit is so tight that its orbital period is predicted to become measurably shorter after only a few years. Burdge's team was able to confirm the prediction from general relativity of a shrinking orbit, by comparing their new results with archival data acquired over the past ten years.
J1539 is a rare gem. It is one of only a few known sources of gravitational waves -- ripples in space and time -- that will be detected by the future European space mission LISA (Laser Interferometer Space Antenna), which is expected to launch in 2034. LISA, in which NASA plays a role, will be similar to the National Science Foundation's ground-based LIGO (Laser Interferometer Gravitational-wave Observatory), which made history in 2015 by making the first direct detection of gravitational waves from a pair of colliding black holes. LISA will detect gravitational waves from space at lower frequencies. J1539 is well matched to LISA; the 4.8 mHz gravitational wave frequency of J1539 is close to the peak of LISA's sensitivity.
Discoveries Continue for Historic Telescope
Kitt Peak's 2.1-meter telescope, the second major telescope to be constructed at the site, has been in continuous operation since 1964. Its history includes many important discoveries in astrophysics, such as the Lyman-alpha forest in quasar spectra, the first gravitational lens by a galaxy, the first pulsating white dwarf, and the first comprehensive study of the binary frequency of stars like the Sun. The latest result continues its venerable track record.
Lori Allen, Director of Kitt Peak National Observatory and Acting Director of NOAO says, "We're thrilled to see that our 2.1-meter telescope, now more than 50 years old, remains a powerful platform for discovery."
"These wonderful observations are further proof that cutting-edge science can be done on modest-sized telescopes like the 2.1-meter in the modern era," adds Chris Davis, NSF Program Officer for NOAO.
More Thrills Ahead!
As remarkable as it is, J1539 was discovered with only a small portion of the data expected from ZTF. It was found in the ZTF team's initial analysis of 10 million sources, whereas the project will eventually study more than a billion stars.
Read more at Science Daily
Supercomputers use graphics processors to solve longstanding turbulence question
Advanced simulations have solved a problem in turbulent fluid flow that could lead to more efficient turbines and engines.
When a fluid, such as water or air, flows fast enough, it will experience turbulence -- seemingly random changes in velocity and pressure within the fluid.
Turbulence is extremely difficult to study but is important for many fields of engineering, such as air flow past wind turbines or jet engines. Understanding turbulence better would allow engineers to design more efficient turbine blades, for example, or make more aerodynamic shapes for Formula 1 cars.
However, current engineering models of turbulence often rely upon 'empirical' relationships based on previous observations of turbulence to predict what will happen, rather than a full understanding of the underlying physics.
This is because the underlying physics is immensely complicated, leaving many questions that seem simple unsolved.
Now, researchers at Imperial College London have used supercomputers, running simulations on graphics processors originally developed for gaming, to solve a longstanding question in turbulence.
Their result, published today in the Journal of Fluid Mechanics, means empirical models can be tested and new models can be created, leading to more optimal designs in engineering.
Co-author Dr Peter Vincent, from the Department of Aeronautics at Imperial, said: "We now have a solution for an important fundamental flow problem. This means we can check empirical models of turbulence against the 'correct' answer, to see how well they are describing what actually happens, or if they need adjusting."
The question is quite simple: if a turbulent fluid is flowing in a channel and it is disturbed, how does that disturbance dissipate in the fluid? For example, if water was suddenly released from a dam into a river and then shut off, what affect would that pulse of dam water have on the flow of the river?
To determine the overall 'average' behaviour of the fluid response, the team needed to simulate the myriad smaller responses within the fluid. They used supercomputers to run thousands of turbulent flow simulations, each requiring billions of calculations to complete.
Using these simulations, they were able to determine the exact parameters that describe how the disturbance dissipates in the flow and determined various requirements that empirical turbulence models must satisfy.
Read more at Science Daily
When a fluid, such as water or air, flows fast enough, it will experience turbulence -- seemingly random changes in velocity and pressure within the fluid.
Turbulence is extremely difficult to study but is important for many fields of engineering, such as air flow past wind turbines or jet engines. Understanding turbulence better would allow engineers to design more efficient turbine blades, for example, or make more aerodynamic shapes for Formula 1 cars.
However, current engineering models of turbulence often rely upon 'empirical' relationships based on previous observations of turbulence to predict what will happen, rather than a full understanding of the underlying physics.
This is because the underlying physics is immensely complicated, leaving many questions that seem simple unsolved.
Now, researchers at Imperial College London have used supercomputers, running simulations on graphics processors originally developed for gaming, to solve a longstanding question in turbulence.
Their result, published today in the Journal of Fluid Mechanics, means empirical models can be tested and new models can be created, leading to more optimal designs in engineering.
Co-author Dr Peter Vincent, from the Department of Aeronautics at Imperial, said: "We now have a solution for an important fundamental flow problem. This means we can check empirical models of turbulence against the 'correct' answer, to see how well they are describing what actually happens, or if they need adjusting."
The question is quite simple: if a turbulent fluid is flowing in a channel and it is disturbed, how does that disturbance dissipate in the fluid? For example, if water was suddenly released from a dam into a river and then shut off, what affect would that pulse of dam water have on the flow of the river?
To determine the overall 'average' behaviour of the fluid response, the team needed to simulate the myriad smaller responses within the fluid. They used supercomputers to run thousands of turbulent flow simulations, each requiring billions of calculations to complete.
Using these simulations, they were able to determine the exact parameters that describe how the disturbance dissipates in the flow and determined various requirements that empirical turbulence models must satisfy.
Read more at Science Daily
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